Process for dyeing cellulosic materials

ABSTRACT

The invention relates to the dyeing of cellulosic materials. Dyeing is effected with the materials, which can be in any form, impregnated with liquid ammonia resulting from a treatment for improving the properties of the cellulosic materials. The dyeaffinity of the materials treated by such a process is generally particularly good, and superior to that of similar materials which have been treated with liquid ammonia but from which the residual ammonia has been removed.

United States Patent [451 July 1, 1975 Dalle PROCESS FOR DYEING CELLULOSIC 3,666,398 5/1972 Tratnyek 8/82 MATERIALS 3,802,835 4/1974 Prieto 8 [75] Inventor: Jean Paul Dalle, Saint Quentin,

France Primary Examiner-Donald Levy [73] Assignee: Omnium de Prospective Industrielle, Attorney Agent or Firm-MEWS Eslmge S.A., Neuville Saint Amand, Aisne, France [22] Filed: May 17, 1973 [57] ABSTRACT 211 App] 3 1,255 The invention relates to the dyeing of cellulosic materials. Dyeing is effected with the materials, which can be in any form, impregnated with liquid ammonia re- [30] Fm'e'gn Apphcamn Pnomy Data sulting from a treatment for improving the properties May 18, I972 France 72.17912 of the cellulosic materials, The dye-affinity of the materials treated by such a process is generally particu- [52] {1.8. C] 8/82; 8/34 lafly good and uperior to that of imilar materials [51] Int. Cl D06p 3/60 which have been treated with liquid ammonia but [58] Fleld of Search 8/82, 34, 54.2 fr which the residual ammonia has beenremoved,

[56] References Cited 7 Claims, N0 Drawings UNITED STATES PATENTS 51 4/1935 Mahn 8/125 PROCESS FOR DYEING CELLULOSIC MATERIALS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the dyeing of cellulosic materials, for example natural or regenerated cellulosic textile materials, either alone or in mixtures, in the form, for example, of filaments, fabrics or any other form.

2. Description of the Prior Art The process of mercerising cellulosic fibres has long been known for improving certain of their properties. This process, which consists of treating the fibers with alcoholic solutions of caustic alkalis, entails numerous practical difficulties.

It has also been proposed to replace this mercerising process by a treatment with liquid ammonia, which is more easy to carry out and gives identical properties or the same improvements as mercerising. It is however, necessary to remove the residual liquid ammonia after this treatment, and different processes have been used, such as washing or heating. However, such processes are expensive and they present difficulties since ammonia has to be removed without causing pollution, and recovery and recycling of a part of this ammonia is required.

As in the case of the classical mercerising, treatment with liquid ammonia improves the dye-affinity of cellulosicfibres, and dyeing according to classical methods is more efficacious if it is effected on a product which has previously been treated with liquid ammonia.

This dye-treatment is effected after the liquid ammonia treatment, all the residual ammonia having previously been removed from the product.

In French Pat. No. 70.36171, it is proposed to carry out a dyeing process in which the material to be dyed is treated with a solution of a coloring agent in liquid ammonia, this treatment being followed by elimination of the residual ammonia. Such a process, which simultaneously causes the ammonia and the coloring agent to act on the material, is inevitably restricted in its conditions of use, such as the temperature of the bath, the duration of treatment, and the type of coloring agent used.

SUMMARY OF THE INVENTION According to. the present invention there is provided a process for dyeing a cellulosic material which process comprises subjecting the material to the action of liquid ammonia to impregnate the material, and effecting dyeing of the liquid ammonia impregnated material.

In accordance with the invention, dyeing is effected without the simultaneous use of liquid ammonia and the residual ammonia introduced during a treatment with liquid ammonia is eliminated during the dyeing. The dye-affinity of the material for the coloring agent is noticeably improved using a process in accordance with the invention, as a result of its being impregnated with liquid ammonia, compared with that of materials after elimination of the residual ammonia.

Dyeing of cellulosic products by a process in accordance with the invention is effected after'the product has been subjected to the action of liquid ammonia. The process of dyeing is, however, effected on a product which is still impregnated with liquid ammonia. Preferably the material is wrung before dyeing to pro- DESCRIPTION OF THE PREFERRED EMBODIMENTS The initial treatment of a cellulosic material, for example a woven cotton cloth, with liquid ammonia can be effected according to a hitherto proposed method. One of the most simple methods is to pass the material through a bath of liquid ammonia maintained at a temperature below 35C at atmospheric pressure.

After leaving the bath, the product, still impregnated with liquid ammonia, is preferably immediately treated with dye, for example by being plunged into abath of a coloring agent. The removal of excess coloring agent, as well as the fixing of the latter on the cellulosic material, can then be effected by known methods.

The use of a process in accordance with the present invention generally serves to improve wetting of cellulosic fibres, and, as a result, their affinity for coloring agents. Penetration to the core of the fibers by the coloring agent can thereby be much more complete and be particularly fast. The coloring of a cellulosic material dyed under these conditions is generally more intense than that of a material dyed after the action of liquid ammonia and the complete elimination of the residual ammonia.

In general, a residual ammonia content of about 30% by weight of the product is sufficient to obtain a satisfactory coloring action. It is often preferred to wring the product between the treatment with liquid ammonia and the abovementioned dyeing in order to recover a part of the ammonia which can be directly recycled. By wringing, the excess ammonia mechanically retained by the product is removed. However, the chemically bound ammonia is not removed.

An attempt will now be made to explain the mechanism by which a process in accordance with the invention improves the cellulosic materials.

The temperature of the dye bath will evidently be varied according to the coloring agent used but it will generally be above that of the liquid ammonia. A fiber impregnated with ammonia when plunged into such a bath of coloring agent is subjected to a sharp rise in temperature which results in a part of the ammonia retained by the material vaporising. This ammonia is released in the gaseous state and it provides an important agitation of the bath in contact with the fiber. The molecules of the coloring agent likely to be absorbed by the material are then constantly renewed at the surface of the material.

The rest of the ammonia, which is soluble in aqueous dye mixtures, dissolves in the dye bath. There are then areas on the treated material which can favour the penetration of the coloring agent.

A chemical reaction also occurs, bonds between the cellulose and the ammonia being broken. This produces reactive sites on the resulting celloglucane, these sites being capable of fixing of a molecule of coloring agent.

These different phenomena simultaneously serve to produce conditions in the cellulosic fiber, and in the dye bath, that permit a rapid elimination of the ammonia and explain the efficacy of the dyeing. It must furthermore be noted that the maintenance of the dye bath at a relatively high temperature, for example, of

at least 20C, generally favours the rapidity of these reactions and it is usually sufficient to eliminate the ammonia which still impregnates the fibres after wringing.

In order to avoid major modifications of the dye bath, it is-necessary constantly to acidify the bath or the bath becomes saturated with ammonia.

Processes in accordance with the present invention can have numerous advantages. They generally do not require modification of conditions of the liquid ammonia treatment. This enables treatment apparatus already installed to be readily used. Wringing enables an important part of the entrained ammonia to be recovered and recycled, without problems of purification and pollution. The separate step of complete elimination of the residual ammonia is also avoided. This represents an economy and it provides an appreciable gain in time. It also avoids the use of washing with water, which necessitated a subsequent purification step in the hitherto proposed processes.

The carrying out of the dyeing can be much easier and effective than hitherto since it can be effected very rapidly, and important gains in raw materials and time can be achieved in obtaining an improved product. Further, it is possible to use a wide range of coloring agents, since the two steps of liquid ammonia treatment and dyeing are effected successively. Such a process can be of particular interest in continuously treating cellulosic materials, such as filaments or weaves, since the number of stages is reduced and the speed of treatment can be noticeably increased.

The following Examples are given by way of illustration only.

Different samples of 280g/m cotton serge were dyed by a process in accordance with the above-described method.

Sample A: dyeing without pre-treatment;

Sample B: pre-treatment in liquid ammonia, evaporation of the ammonia in a current of hot air, and

dyeing;

Sample C: pre-treatment with liquid ammonia, wringing until about 40% by weight of residual ammonia, and dyeing;

Sample D: pre-treatment with liquid ammonia, then dyeing without removal of any of the ammonia.

EXAMPLE I Dyeing was effected under the same conditions for each sample by immersing them for about ten seconds in a dye-bath maintained at a temperature of about 60C. The dye-bath had the following composition:

coloring agent Solane Blue R (powder) 7g/l sodium hydrosulphite ISg/l soda of 36 Be 30cc/l.

Solane Blue R is a vat-dye of formula Subsequent removal of the product from the bath and oxidation in an oxygenated medium was effected. After rinsing, the product was washed by boiling with 2.5g/l of sodium carbonate and 2g/l of sodium lauryl sulfate.

Examination of each sample showed that the coloring of samples C and D, dyed when they contained ammonia, was darker than that of sample B which was .dyed when it contained no ammonia. However, a prolonged dyeing time did not provide a sample B equivalent to samples C or D. Regarding sample A, a dyeing time as short as that which produced satisfactory results with other samples, the bath containing a small quantity of coloring agent, did not give satisfactory results.

Comparison of the results of the dyeing gave a ratio of l to 3 between samples A and B, and a ratio of l to 6 between samples A and C or D.

EXAMPLE 2 Dyeing was effected by immersion for about one minute in a dye-bath, maintained at 50C. The bath had the following composition:

blue-dye S.B.A. 3g/l sodium hydrosulphite 6.25g/l soda of 36 Be l2.5cc/l.

Blue dye S.B.A. conforms to a formula of the following chemical type In this case, oxidation had to be effected in a neutral medium in order to avoid changes in color. Processing was then by rinsing the product after dyeing and subsequent oxidation in a mixture of oxygenated water and acetic acid.

Such a treatment gave results substantially identical to those of Example 1.

I claim:

1. A process for the dyeing of a material composed of cellulosic fibers deep colors, which process comprises treating said material in a bath of liquid ammonia to impregnate the fibers of said material with said ammonia, and thereafter dyeing the ammoniaimpregnated fibers of said material in an aqueous dyebath containing a dyestuff for said cellulosic fibers.

2. A process according to claim 1 wherein said ammonia-impregnated cellulosic fibers of said material have up to about 40% of ammonia by weight of fiber.

3. A process according to claim 2 which further comprises removing ammonia from said ammoniaimpregnated fibers prior to dyeing thereof to adjust the amount of ammonia.

4. A process according to claim 3 wherein said ammonia is removed by wringing said material.

6 of liquid ammonia is maintained at atmospheric pressure at a temperature below about -35C., and said dyebath is maintained at a temperature above about 20C. whereby ammonia is removed from said ammonia-impregnated fibers in said dyebath.

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,892,52l I Dated July 1, 1975 Inventor(s) Jean Paul Dalle It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading, change:

[30] May 18, 1972 France .."72.179l2" [30] May 18, 1972 France. .--72.17922-- Signed and Scalcd this [SEAL] twemy'thid D f December 1975 A ttest:

R A53? CgiSON C. MARSHALL DANN s mg jjlc'er Commissioner of Parents and Trademarks 

1. A PROCESS FOR THE DYEING OF A MATERIAL COMPOSED OF CELLULOSIC FIBERS DEEP COLORS, WHICH PROCESS COMPRISES TREATING SAID MATERIAL IN A BATH OF LIQUID AMMONIA TO IMPREGNATE THE FIBERS OF SAID MATERIAL WITH SAID AMMONIA, AND THEREAFTER DYEING THE AMMONIA-IMPREGNATED FIBERS OF SAID MATERIAL IN AN AQUEOUS DYEBATH CONTAINING A DYESTUFF FOR SAID CELLULOSIC FIBERS.
 2. A process according to claim 1 wherein said ammonia-impregnated cellulosic fibers of said material have up to about 40% of ammonia by weight of fiber.
 3. A process according to claim 2 which further comprises removing ammonia from said ammonia-impregnated fibers prior to dyeing thereof to adjust the amount of ammonia.
 4. A process according to claim 3 wherein said ammonia is removed by wringing said material.
 5. A process according to claim 1 wherein said ammonia-impregnated cellulosic fibers of said material have about 30% of ammonia by weight of fiber.
 6. A process according to claim 5 wherein ammonia is removed from said ammonia-impregnated fibers by wringing to adjust the amount of ammonia.
 7. A process according to claim 1 wherein said bath of liquid ammonia is maintained at atmospheric pressure at a temperature below about -35*C., and said dyebath is maintained at a temperature above about 20*C. whereby ammonia is removed from said ammonia-impregnated fibers in said dyebath. 